/*
 * QEMU Block backends
 *
 * Copyright (C) 2014 Red Hat, Inc.
 *
 * Authors:
 *  Markus Armbruster <armbru@redhat.com>,
 *
 * This work is licensed under the terms of the GNU LGPL, version 2.1
 * or later.  See the COPYING.LIB file in the top-level directory.
 */

#include "sysemu/block-backend.h"
#include "block/block_int.h"
#include "block/blockjob.h"
#include "block/throttle-groups.h"
#include "sysemu/blockdev.h"
#include "sysemu/sysemu.h"
//#include "qapi-event.h"

/* Number of coroutines to reserve per attached device model */
#define COROUTINE_POOL_RESERVATION 64

static AioContext *blk_aiocb_get_aio_context(BlockAIOCB *acb);

struct BlockBackend {
    char *name;
    int refcnt;
    BlockDriverState *bs;
    DriveInfo *legacy_dinfo;    /* null unless created by drive_new() */
    QTAILQ_ENTRY(BlockBackend) link; /* for blk_backends */

    void *dev;                  /* attached device model, if any */
    /* TODO change to DeviceState when all users are qdevified */
    const BlockDevOps *dev_ops;
    void *dev_opaque;

    /* the block size for which the guest device expects atomicity */
    int guest_block_size;

    /* If the BDS tree is removed, some of its options are stored here (which
     * can be used to restore those options in the new BDS on insert) */
    BlockBackendRootState root_state;

    /* I/O stats (display with "info blockstats"). */
    BlockAcctStats stats;

    BlockdevOnError on_read_error, on_write_error;
    bool iostatus_enabled;
    BlockDeviceIoStatus iostatus;
};

typedef struct BlockBackendAIOCB {
    BlockAIOCB common;
    QEMUBH *bh;
    BlockBackend *blk;
    int ret;
} BlockBackendAIOCB;

static const AIOCBInfo block_backend_aiocb_info = {
    .get_aio_context = blk_aiocb_get_aio_context,
    .aiocb_size = sizeof(BlockBackendAIOCB),
};

static void drive_info_del(DriveInfo *dinfo);

/* All the BlockBackends (except for hidden ones) */
static QTAILQ_HEAD(, BlockBackend) blk_backends =
    QTAILQ_HEAD_INITIALIZER(blk_backends);



static void blk_delete(BlockBackend *blk)
{
    assert(!blk->refcnt);
    assert(!blk->dev);
    if (blk->bs) {
        assert(blk->bs->blk == blk);
        blk->bs->blk = NULL;
        bdrv_unref(blk->bs);
        blk->bs = NULL;
    }
    if (blk->root_state.throttle_state) {
        g_free(blk->root_state.throttle_group);
        throttle_group_unref(blk->root_state.throttle_state);
    }
    /* Avoid double-remove after blk_hide_on_behalf_of_hmp_drive_del() */
    if (blk->name[0]) {
        QTAILQ_REMOVE(&blk_backends, blk, link);
    }
    g_free(blk->name);
    drive_info_del(blk->legacy_dinfo);
    block_acct_cleanup(&blk->stats);
    g_free(blk);
}

static void drive_info_del(DriveInfo *dinfo)
{
    if (!dinfo) {
        return;
    }
    qemu_opts_del(dinfo->opts);
    g_free(dinfo->serial);
    g_free(dinfo);
}

int blk_get_refcnt(BlockBackend *blk)
{
    return blk ? blk->refcnt : 0;
}

/*
 * Increment @blk's reference count.
 * @blk must not be null.
 */
void blk_ref(BlockBackend *blk)
{
    blk->refcnt++;
}

/*
 * Decrement @blk's reference count.
 * If this drops it to zero, destroy @blk.
 * For convenience, do nothing if @blk is null.
 */
void blk_unref(BlockBackend *blk)
{
    if (blk) {
        assert(blk->refcnt > 0);
        if (!--blk->refcnt) {
            blk_delete(blk);
        }
    }
}

/*
 * Return the BlockBackend after @blk.
 * If @blk is null, return the first one.
 * Else, return @blk's next sibling, which may be null.
 *
 * To iterate over all BlockBackends, do
 * for (blk = blk_next(NULL); blk; blk = blk_next(blk)) {
 *     ...
 * }
 */
BlockBackend *blk_next(BlockBackend *blk)
{
    return blk ? QTAILQ_NEXT(blk, link) : QTAILQ_FIRST(&blk_backends);
}

/*
 * Return @blk's name, a non-null string.
 * Wart: the name is empty iff @blk has been hidden with
 * blk_hide_on_behalf_of_hmp_drive_del().
 */
const char *blk_name(BlockBackend *blk)
{
    return blk->name;
}

/*
 * Return the BlockBackend with name @name if it exists, else null.
 * @name must not be null.
 */
BlockBackend *blk_by_name(const char *name)
{
    BlockBackend *blk;

    assert(name);
    QTAILQ_FOREACH(blk, &blk_backends, link) {
        if (!strcmp(name, blk->name)) {
            return blk;
        }
    }
    return NULL;
}

/*
 * Return @blk's DriveInfo if any, else null.
 */
DriveInfo *blk_legacy_dinfo(BlockBackend *blk)
{
    return blk->legacy_dinfo;
}

/*
 * Set @blk's DriveInfo to @dinfo, and return it.
 * @blk must not have a DriveInfo set already.
 * No other BlockBackend may have the same DriveInfo set.
 */
DriveInfo *blk_set_legacy_dinfo(BlockBackend *blk, DriveInfo *dinfo)
{
    assert(!blk->legacy_dinfo);
    return blk->legacy_dinfo = dinfo;
}

/*
 * Return the BlockBackend with DriveInfo @dinfo.
 * It must exist.
 */
BlockBackend *blk_by_legacy_dinfo(DriveInfo *dinfo)
{
    BlockBackend *blk;

    QTAILQ_FOREACH(blk, &blk_backends, link) {
        if (blk->legacy_dinfo == dinfo) {
            return blk;
        }
    }
    abort();
}

/*
 * Attach device model @dev to @blk.
 * Return 0 on success, -EBUSY when a device model is attached already.
 */
int blk_attach_dev(BlockBackend *blk, void *dev)
/* TODO change to DeviceState *dev when all users are qdevified */
{
    if (blk->dev) {
        return -EBUSY;
    }
    blk_ref(blk);
    blk->dev = dev;
    blk_iostatus_reset(blk);
    return 0;
}

/*
 * Detach device model @dev from @blk.
 * @dev must be currently attached to @blk.
 */
void blk_detach_dev(BlockBackend *blk, void *dev)
/* TODO change to DeviceState *dev when all users are qdevified */
{
    assert(blk->dev == dev);
    blk->dev = NULL;
    blk->dev_ops = NULL;
    blk->dev_opaque = NULL;
    blk->guest_block_size = 512;
    blk_unref(blk);
}

/*
 * Return the device model attached to @blk if any, else null.
 */
void *blk_get_attached_dev(BlockBackend *blk)
/* TODO change to return DeviceState * when all users are qdevified */
{
    return blk->dev;
}

/*
 * Set @blk's device model callbacks to @ops.
 * @opaque is the opaque argument to pass to the callbacks.
 * This is for use by device models.
 */
void blk_set_dev_ops(BlockBackend *blk, const BlockDevOps *ops,
                     void *opaque)
{
    blk->dev_ops = ops;
    blk->dev_opaque = opaque;
}

/*
 * Notify @blk's attached device model of media change.
 * If @load is true, notify of media load.
 * Else, notify of media eject.
 * Also send DEVICE_TRAY_MOVED events as appropriate.
 */
void blk_dev_change_media_cb(BlockBackend *blk, bool load)
{
    if (blk->dev_ops && blk->dev_ops->change_media_cb) {
        bool tray_was_open, tray_is_open;

        tray_was_open = blk_dev_is_tray_open(blk);
        blk->dev_ops->change_media_cb(blk->dev_opaque, load);
        tray_is_open = blk_dev_is_tray_open(blk);

        if (tray_was_open != tray_is_open) {
            //qapi_event_send_device_tray_moved(blk_name(blk), tray_is_open,
            //                                  &error_abort);
        }
    }
}

/*
 * Does @blk's attached device model have a tray, and is it open?
 */
bool blk_dev_is_tray_open(BlockBackend *blk)
{
    if (blk->dev_ops && blk->dev_ops->is_tray_open) {
        return blk->dev_ops->is_tray_open(blk->dev_opaque);
    }
    return false;
}

/*
 * Does @blk's attached device model have the medium locked?
 * %false if the device model has no such lock.
 */
bool blk_dev_is_medium_locked(BlockBackend *blk)
{
    if (blk->dev_ops && blk->dev_ops->is_medium_locked) {
        return blk->dev_ops->is_medium_locked(blk->dev_opaque);
    }
    return false;
}

/*
 * Notify @blk's attached device model of a backend size change.
 */
void blk_dev_resize_cb(BlockBackend *blk)
{
    if (blk->dev_ops && blk->dev_ops->resize_cb) {
        blk->dev_ops->resize_cb(blk->dev_opaque);
    }
}

void blk_iostatus_enable(BlockBackend *blk)
{
    blk->iostatus_enabled = true;
    blk->iostatus = BLOCK_DEVICE_IO_STATUS_OK;
}

/* The I/O status is only enabled if the drive explicitly
 * enables it _and_ the VM is configured to stop on errors */
bool blk_iostatus_is_enabled(const BlockBackend *blk)
{
    return (blk->iostatus_enabled &&
           (blk->on_write_error == BLOCKDEV_ON_ERROR_ENOSPC ||
            blk->on_write_error == BLOCKDEV_ON_ERROR_STOP   ||
            blk->on_read_error == BLOCKDEV_ON_ERROR_STOP));
}

BlockDeviceIoStatus blk_iostatus(const BlockBackend *blk)
{
    return blk->iostatus;
}

void blk_iostatus_disable(BlockBackend *blk)
{
    blk->iostatus_enabled = false;
}

void blk_iostatus_reset(BlockBackend *blk)
{
    if (blk_iostatus_is_enabled(blk)) {
        blk->iostatus = BLOCK_DEVICE_IO_STATUS_OK;
        if (blk->bs && blk->bs->job) {
            block_job_iostatus_reset(blk->bs->job);
        }
    }
}

static int blk_check_byte_request(BlockBackend *blk, int64_t offset,
                                  size_t size)
{
    int64_t len;

    if (size > INT_MAX) {
        return -EIO;
    }

    if (!blk_is_available(blk)) {
        return -ENOMEDIUM;
    }

    len = blk_getlength(blk);
    if (len < 0) {
        return len;
    }

    if (offset < 0) {
        return -EIO;
    }

    if (offset > len || len - offset < size) {
        return -EIO;
    }

    return 0;
}

static int blk_check_request(BlockBackend *blk, int64_t sector_num,
                             int nb_sectors)
{
    if (sector_num < 0 || sector_num > INT64_MAX / BDRV_SECTOR_SIZE) {
        return -EIO;
    }

    if (nb_sectors < 0 || nb_sectors > INT_MAX / BDRV_SECTOR_SIZE) {
        return -EIO;
    }

    return blk_check_byte_request(blk, sector_num * BDRV_SECTOR_SIZE,
                                  nb_sectors * BDRV_SECTOR_SIZE);
}

int blk_read(BlockBackend *blk, int64_t sector_num, uint8_t *buf,
             int nb_sectors)
{
    int ret = blk_check_request(blk, sector_num, nb_sectors);
    if (ret < 0) {
        return ret;
    }

    return bdrv_read(blk->bs, sector_num, buf, nb_sectors);
}

int blk_write(BlockBackend *blk, int64_t sector_num, const uint8_t *buf,
              int nb_sectors)
{
    int ret = blk_check_request(blk, sector_num, nb_sectors);
    if (ret < 0) {
        return ret;
    }

    return bdrv_write(blk->bs, sector_num, buf, nb_sectors);
}

int64_t blk_getlength(BlockBackend *blk)
{
    if (!blk_is_available(blk)) {
        return -ENOMEDIUM;
    }

    return bdrv_getlength(blk->bs);
}

int blk_is_read_only(BlockBackend *blk)
{
    if (blk->bs) {
        return bdrv_is_read_only(blk->bs);
    } else {
        return blk->root_state.read_only;
    }
}

bool blk_is_inserted(BlockBackend *blk)
{
    return blk->bs && bdrv_is_inserted(blk->bs);
}

bool blk_is_available(BlockBackend *blk)
{
    return blk_is_inserted(blk) && !blk_dev_is_tray_open(blk);
}

AioContext *blk_get_aio_context(BlockBackend *blk)
{
    if (blk->bs) {
        return bdrv_get_aio_context(blk->bs);
    } else {
        return qemu_get_aio_context();
    }
}

static AioContext *blk_aiocb_get_aio_context(BlockAIOCB *acb)
{
    BlockBackendAIOCB *blk_acb = DO_UPCAST(BlockBackendAIOCB, common, acb);
    return blk_get_aio_context(blk_acb->blk);
}
